Configuring Unidirectional Link Routing
UDLR Overview
IPC-507
Cisco IOS IP Configuration Guide
In a large enterprise network, it is not possible to be able to receive IP multicast traffic via satellite and
forward the traffic throughout the network. This limitation exists because receiving hosts must be
directly connected to the downstream router. However, you can use the IGMP Proxy mechanism to
overcome this limitation. See the “IGMP Proxy” section later in this chapter for more information on
this mechanism.
For information on IGMP, refer to the “Configuring IP Multicast Routing” chapter in the Cisco IOS IP
Configuration Guide.
IGMP Proxy
The IGMP Proxy mechanism enables hosts that are not directly connected to a downstream router to join
a multicast group sourced from an upstream network. Figure82 illustrates this mechanism.
Figure82 IGMP Mroute Proxy Mechanism
Router A
Router B
Unidirectional link
Unidirectional
tunnel
LAN B RP
Internet
Local net
Router C
User 1
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